Showing posts with label deposition. Show all posts
Showing posts with label deposition. Show all posts

Saturday, February 20, 2010

Unconformity

LinkGrand.com

a break in the deposition of sedimentary rocks, allowing erosion of previously formed rock before eventual deposition of further sediments. It is usually represented by an obvious difference in the attitude of the rocks on either side of the unconformity, with the upper lying unconformably on the lower.

Taken from Dictionary of Science

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An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic record. The phenomenon of angular unconformity (see below) was discovered by James Hutton, who found examples at Jedburgh in 1787 and at Siccar Point in 1788.


The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is called a hiatus.


Taken from Wikipedia




Wednesday, December 30, 2009

Kame


a structure produced by glacial deposition. It occurs as a mound of sands and gravels, with bedding (that is, it is arranged in layers) and often slumping at the sides. It was formed by the melting of stagnant ice which as a result dropped its load of sediment.

Taken from Dictionary of Science

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A kame is a geological feature, an irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier. Kames are often associated with kettles, and this is referred to as kame and kettle topography.

Taken from Wikipedia